I was playing with some free backlinks checker tools when I found the same recurring shady websites in the results.

You can see some of them by searching "Open Source Keyword Rankings" (with quotes) on Google and looking at the last results. Some examples: 'drjack.world', 'bye.fyi'. I'm not posting here the full URLs.

Their home pages are a simple list of serch keyword in the form of internal webpage links. They point to a page dedicated to each keyword (e.g. 'bye.fyi/keyword-ranking/1127933/what+is+qjv') which prompts you to navigate to an online paid SEO tool.

If you run some searches on those domains, it's easy to see they were used for something else some time ago, then they expired and were acquired to be used in this advertising scheme.

Basically this means that when someone uses backlinks checkers, he can end up to this paid SEO tool, kind of an ad injection into their competitors service. Is this the only benefit of the scheme or is there something else I'm missing?